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DER IntegrationEmerging system security challenges in South Australia
About AEMOAEMO operates Australia's National Electricity Market and power grid in Australia’s eastern and south-eastern seaboard, and the Wholesale Electricity Market and power grid in south-west WA.
Both markets supply more than 220 terawatt hours of electricity each year.
We also operate retail and wholesale gas markets across south-eastern Australia and Victoria’s gas pipeline grid.
Collectively NEM & WEM traded over A$20 billion in the last financial year.
Ownership
Marketparticipants
40%Governments of Australia
60%
2
Resource development outlook
High DER scenario
Distributed PV
AEMO (12 Dec 2019) Draft 2020 Integrated System Plan, at https://aemo.com.au/-/media/files/electricity/nem/planning_and_forecasting/isp/2019/draft-2020-integrated-system-plan.pdf?la=en
~85% of electrical load in Australia
National Electricity Market (NEM)
1 – 3 GW
Heywood Interconnector
South Australia – DER integration
5
• Within 1-3 years, operational demand in South Australia could become negative.
• When and what operational challenges may arise?
• What actions do we need to take now, to ensure we can operate a secure system?
• Primary focus of DER Program Operations Stream
Distributed PV
Minimum operational demand in SA
Agenda• Preliminary
findings and recommended actions
https://aemo.com.au/-/media/files/electricity/nem/planning_and_forecasting/sa_advisory/2020/minimum-operational-demand-thresholds-in-south-australia-review.pdf?la=en
Appendix A, at: https://aemo.com.au/-/media/files/stakeholder_consultation/consultations/nem-consultations/2020/psfrr/psfrr-stage-1.pdf?la=en
Preliminary findings
Distributed PV disconnection
Minimum load required to operate under islanded conditions
Under Frequency Load Shedding
Challenges identified:
Distributed PV disconnection• Analysis of PV disconnection
based upon data from individual inverters
• Verified by bench testing (ARENA project with UNSW)
• Used to calibrate PSS®E model of DER behaviour
• PSS®E studies of a severe but credible fault in the Adelaide metropolitan area:
• 19 - 20% of underlying load in SA disconnects
• 38 - 44% of distributed PV generation in SA disconnects
Distributed PV disconnection observed
Distributed PV disconnection• Severe but credible fault near Adelaide
metropolitan area could cause significant disconnection of distributed PV
• Increases largest credible contingency• Added to largest generating unit
• Constraint introduced to manage risks of separation/triggering SIPS
• When operating as an SA island:• Becomes almost impossible to maintain
frequency >49Hz when DER-load loss exceeds ~150 MW (may be operating in this realm in some periods already)
• AEMO may no longer have the ability to operate SA in a secure state, if islanding occurs at times of high distributed PV generation
Maximum net PV disconnection (SA)
Measures to manage PV disconnection
1. Improve DER standards (AS4777)• https://sapc.standards.org.au/sapc/public/listOpenCommenting
Publication.action
2. Accelerated voltage ride through test in SA• https://aemo.com.au/en/consultations/current-and-closed-
consultations/short-duration-undervoltage-disturbance-ride-through-test-procedure
3. Improve compliance with standards
4. Collaborate with DNSPs on connection requirements
5. EnergyConnect (new AC interconnector SA-NSW)
6. Network constraints
Minimum demand threshold• Islanded operation: Need
adequate load to operate necessary units for system strength, inertia, frequency control and voltage management
• Lowest operational demand experienced: 458 MW (10 Nov 2019)
• 2019 was a “moderate” year –minimum demand can become very low with:
• Sunny• Mild temperatures, on• Spring/Summer public holidays
Minimum operational demand in SA
Measures for islanded operation with low load1. SAPN: Flexible Exports – longer term, sophisticated, supports market
integration and distribution management2. PV shedding – immediate, simple, robust, supports system security
• Analogous to load shedding• Anticipate use only during abnormal conditions, eg. islanding, line outages, etc.• Identified options that meet requirements:
• Enhanced voltage management• Smart Meters
Under Frequency Load Shedding• UFLS designed to arrest severe under-frequency
events• Separation events• Multiple contingency events
• Security challenges identified:1. Reducing net load2. Reverse flows3. Distributed PV disconnection
• Incidence of risk forecast to increase in SA post syncon commissioning
• Actions:• Increase UFLS load• Dynamic arming of UFLS relays• Heywood constraint• Protected event submission• NER review
• Consultation:• https://aemo.com.au/consultations/current-and-
closed-consultations/2020-psfrr-consultation
PV tripping
UFLS Load (MW)
Heyw
ood
Impo
rt (M
W)
Next steps
• Collaboration with stakeholders on design and implementation of mitigation actions
• Analysis for other NEM regions underway1. PV disconnection and impact on contingency sizes2. Minimum load required for islanded operation (QLD)3. UFLS – data request for NSPs
• Continuing development of tools and data• Models in PSSE/PSCAD, rollout for stakeholders• Improving data on DER behavior (Solar Analytics, UNSW, ARENA)
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